The present invention relates to an exposure device incorporated into an image forming apparatus, such as a copier and printer, and, in particular, to a structure for adjusting the tilt of an exposure device relative to a photosensitive drum.
An image forming apparatus, such as a copier or printer, includes an exposure device for scanning, with exposure light, the surface of a photosensitive drum to form an electrostatic latent image on the drum surface. The exposure device includes a laser beam source for emitting a laser beam based on image data and a polygon mirror for deflecting the laser beam toward a main scanning direction to allow the drum surface to be scanned with the exposure light. That is, the laser beam is deflected toward the main scanning direction by rotating the polygon mirror and the electrostatic latent image based on the image data is formed on the drum surface by rotating the photosensitive drum in a sub-scanning direction.
In order to prevent a tilt from being produced on the electrostatic latent image formed on the drum surface, the tilt of the exposure device relative to the photosensitive drum is adjusted on shipment and installation of the device. In this case, in order to make a narrower linear exposure light spot which is formed on the drum surface by the laser beam scanned toward the main scanning direction parallel to the rotation shaft of the photosensitive drum, the exposure device as a whole is rotated about a predetermined rotation shaft.
If, in this way, the exposure device is rotated, it is possible to correct the tilt of the exposure light spot formed on the drum surface. However, the scanning start position corresponding to the end of the exposure light spot is also displaced toward the rotation shaft direction of the photosensitive drum, presenting a problem.